At the time of the start of the Winter War, Mildh was assigned to LLv 26.

On 23 December, a patrol led by luutnantti Pentti Tevä took off on an interception mission towards Lake Laatokka (Ladoga). Over Käkisalmi at 11:55, they encountered a formation of 6 to 7 SBs from 24 SBAP, which were bombing from the altitude of 1700 m and 100 meters above clouds. Tevä shot one down and it crashed into the Lake Ladoga confirmed by the coastal units. Lentomestari Mildh dove after the formation but could not gain enough speed until surprisingly one SB passed beneath him. He had an opportunity to fire at the SB for several minutes. The SB received hits and dove steep into a low-lying cloud and Mildh was credited with a damaged aircraft.

Mildh claimed one damaged victory during the war, this one being claimed while flying Bristol Bulldog.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1939
	23/12/39	11:55-12:00	1	SB (a)	Damaged	Bulldog	BU-74	Käkisalmi	LLv 26

Biplane victories:1 damaged.
TOTAL: 1 damaged.
(a) Claimed in combat with SBs from 24 SBAP.

Sources:
Ilmavoitot, osa 2 - Kalevi Keskinen and Kari Stenman, ISBN 952-99432-8-8
Information kindly provided by Tuomo Lukkari and Pentti Perttula.